Renal Physiology Refresher- Liang Flashcards
Where is the water in the body stored? What separates these compartments? What connects them?
2/3- Intracellular Fluid
1/3- Extracellular Fluid (25% plasma, 75% Interstitial)
Cell membrane separates intra- and extracellular fluid while capillary membrane separates plasma from interstitial.
Lymphatics connects plasma and interstitial.
Which solutes are found in extracellular fluids and which in intracellular fluids?
Extracellular- Na, Cl, HCO3
Intracellular- K, Phosphate, Protein
What is the difference between osmolarity and osmolality?
At dilute concentrations, nothing.
osmolarity- mosm/ LITER OF WATER
osmolality- mosm/KILOGRAM OF WATER
What is the osmolarity of the solutions in the body?
280-300 mosm/liter
What are the four steps that determine the composition of the urine?
1) filtration
2) absorption
3) secretion
4) excretion
Where does filtration occur? What does the “urine” look like at this time?
Glomerular apparatus
“Urine” is basically acellular plasma, contains proteins, solutes, sugars, etc
How is the filtration pressure calculated?
filtration pressure= glomerular hydrostatic pressure-(bowman’s capsule hydrostatic pressure+ glomerular colloid pressure)
What is the ultrafiltration coefficient? What determines its value?
translates the net pressure into permeability
determined by podocyte foot structure and surface area of glomerular capillaries
How variable is the GFR and renal perfusion?
What controls GFR and renal perfusion?
stable except at very low or very high pressures
myogenic response, tubuloglomerular feedback
What is the myogenic response?
Intrinsic to smooth muscle cells in the arteries, when blood pressure rises, smooth muscles constrict and increase resistance.
What is tubuloglomerular feedback?
With increased perfusion, more sodium enters the macula densa. At high concentrations of sodium, the macula densa causes afferent constriction and decreased renin release, leading to decreased GFR.
What are the layers of the capillaries in the glomerular apparatus?
- podocyte feet
- basement membrane with negatively charged polymer proteins (collagen, laminin, etc)
- fenestrated endothelium with negatively charged glycocalyx
TLDR: charge-selective and size-selective
What occurs in the thin descending loop of Henle?
Water reabsorption
What occurs in the thin ascending loop of Henle?
Passive reabsorption of sodium
secretion of urea
What occurs in the thick ascending loop of Henle?
Reabsorption of Na by Na/K/2 Cl transporter
passive, paracellular absorption of positive ions
secretion of H
Water impermeable
What drug inhibits the Na/K/2Cl co-transporter?
Loop diuretics
What happens in the early distal tubule?
Resorbs Na, Cl, Ca, and Mg
Na/Cl co transporter
Water impermeable
What drug acts on the early distal tubule?
Thiazide diuretics
It inhibits the Na/Cl co-transporter
What happens in the late distal tubule and cortical collecting tube?
Na resorption/K secretion- aldosterone
Water resorption- ADH
What drug works in the late distal tubule and cortical collecting tube?
Potassium sparing diuretics
Aldosterone antagonists
What happens in the medullary collecting tubes?
Resorbs sodium
Water resorption- ADH
Urea resorption
What does aldosterone do? Where does it act?
Aldosterone upregulates ENaC channels to resorb Na and secrete K
Acts in the late distal tubule and collecting duct
What does angiotensin II do? Where does it act?
Angiotensin II upregulates Na/H antiporter activity to resorb sodium, secrete H
Acts in the proximal tubule
What does ADH do? Where does it act?
Inserts aquaporins to increase water absorption
Acts in late distal tubule, cortical and medullary collecting duct
What does ANP do? Where does it act?
It decreases Na resorption by phosphorylating the ENaC channels to inactivate them
Acts in the distal tubule and collecting duct
What does parathyroid hormone do? Where does it act?
It decreases phosphate resorption and increases calcium resorption
Phosphate effects happen in the proximal tubule, calcium happens in the ascending loop of Henle and distal tubule
